Deformation twinning of ferrocene crystals assisted by the rotational mobility of cyclopentadienyl rings.

Deformation twinning, which is a type of plastic deformation, has been particularly investigated in metal materials. However, only a few examples are found in organic solids. We observed mechanical twinning deformation on a simple ferrocene crystal, which is considered the most representative organometallic compound, and evaluated the crystal structures under the twinning state and the shear deformation characteristics by single-crystal X-ray diffraction analysis and uniaxial compression tests. The structural analyses showed the molecular rearrangement during twinning deformation. The shear deformation properties depend on the rotational mobility of the cyclopentadienyl rings in comparison with crystals of nickelocene, ruthenocene, and mixed crystals of ferrocene/ruthenocene.